The pH is determined to identify the reaction of substance which may be either acidic, neutral or alkaline. Specifically, the pH is indicative of the concetration of H+ ion present in a solution.
Principle
An acid-base electrode (pH sensitive electrode) is used to measured the pH of a suspension of the powder to be tested, or of a pulp sample in demineralized water.
For pulp samples and slurries, pH is usualy measured directly and very after the value has been preset for a given concentration.
Or the pH value of paper can be determined by:
Disintegrating the paper in hot distilled water and determining the pH of the extract.
Disintegrating the paper in cold distilled water and determining the pH of the extract.
Directly using a wet electrode on the paper surface.
These 3 methods measure different solutions and so give different
The pH value of paper can show residual acidic/alkaline chemicals in pulp, or atmospheric pollutants (e.g. SO2) in valuable paper archives.
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